This paper presents a case of the application of Computed Tomography (CT) technology on detection of underground solution features and cavities for a commercial development site in WuXi, People Republic of China. Three high-rise commercial buildings of height 340m, 155m and 90m respectively, with a basement of 20m deep were proposed to be constructed. From the results of preliminary and detailed ground investigation, it was revealed that the rock head was about 85m below ground. However, solution features and cavities of various sizes were present in the first 60m below the rock head level. Such solution features and cavities are vulnerable and prone to collapse when subjected to the imposed building loads.

In order to delineate the spatial locations and sizes of these solution features and cavities probably present in bedrock under the footprints of the proposed buildings, two different geophysical surveys, namely Seismic Wave CT method and Electromagnetic Wave CT method, were carried out on site. With the aid of computed tomography technology, the large amount of spatial survey data were woven together to make images of the underground anomalies, and hence provided information on their locations and sizes for foundation design engineer to get over this complex foundation problem.